Internal combustion engine manufacturers are constantly seeking to increase power output and fuel efficiency of their products. One method of generally increasing efficiency and power is to reduce the oscillating mass of an engine, e.g., of the pistons, connecting rods, and other moving parts of the engine. Engine power may also be increased by raising the compression ratio of the engine. Raising the compression ratio of an engine also generally raises the pressure and temperature within the combustion chamber during operation.
Engines, and in particular the pistons, are therefore under increased stress as a result of these reductions in weight and increased pressures and temperatures associated with engine operation. Piston cooling is therefore increasingly important for withstanding the increased stress of such operational conditions over the life of the engine.
To reduce the operating temperatures of piston components, a cooling gallery may be provided about a perimeter of the piston. Crankcase oil may be introduced to the cooling gallery, and may be distributed about the cooling gallery by the reciprocating motion of the piston, thereby reducing the operating temperature of the piston.
At the same time, the cooling galleries may increase the size and overall complexity of the piston assembly. For example, cooling galleries may require additional parts, such as cooling gallery covers, in order to encourage proper circulation of a coolant throughout the cooling gallery. Some piston designs may also employ a cover plate fitted to the piston crown that generally traps oil within the cooling gallery, thereby increasing the cooling effect of the gallery.
Accordingly, there is a need for a piston that minimizes overall piston weight and complexity, while also allowing adequate cooling, such as by providing a cooling gallery.